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4 1 multiplying rational numbers examples
1. multiply rational numbers.
SOL: none
Objective
The student will be able to:
Designed by Skip Tyler, Varina High School and Nicole Kessinger Deep Run High School
2. Multiplying Rules
1) If the numbers have the same
signs then the product is positive.
(-7) • (-4) = 28
2) If the numbers have different
signs then the product is negative.
(-7) • 4 = -28
3. Examples
1) (3x)(-8y)
−20( )
4
5
2) Write both numbers as a fraction.
Cross-cancel if possible.
−
20
1
4
5
−
80
5
= -16
Multiplying fractions:
top # • top #
Bottom # • bottom#
-24xy
6. an easy way to determine the sign of the answer
3 negative signs -> Odd -> answer is negative
-480
When you have an odd number of negatives,
the answer is negative.
When you have an even number of negatives,
the answer is positive.
4) (-2)(-8)(3)(-10)
Do you have an even or odd number of
negative signs?